President Bush's decision to allow the super-secret National Security Agency to spy on Americans without court warrants has touched off stormy debate about his aggressive approach to the war on terror.

This clash - between civil libertarians and the administration's expansive view of presidential power - is a recurring theme in the Bush White House. It lies at the center of ongoing debates over the government's use of coercive interrogation techniques and the open-ended detention of alleged enemy combatants at Guantánamo Bay, Cuba, and in military prisons in the United States.

This week, the spotlight is on a recently disclosed classified operation that permits the NSA to monitor communications between suspected Al Qaeda members overseas and American citizens in the US. It is being done without first obtaining a warrant from a special intelligence court set up to police such sensitive intercepts.

Instead of following the safeguards established by Congress under the 1978 Foreign Intelligence Surveillance Act (FISA), Bush administration lawyers concluded that the White House could sidestep the warrant requirements while conducting the espionage operation.

Critics say the secret spying is illegal and an abuse of the president's constitutional authority. Supporters say Bush is well within his power to protect the nation from terrorists.

Disclosure of the NSA operation by the New York Times last Friday surprised many members of Congress and is said to have complicated efforts to reauthorize the Patriot Act. Republican Sen. Arlen Specter, chairman of the Judiciary Committee, has called for hearings to look into the NSA operation. Supreme Court nominee Samuel Alito has been warned to prepare for close questioning on the matter in his upcoming confirmation hearing. And there is talk of the possible appointment of two special counsels, one to look into the legality of the NSA operation, the other to investigate the disclosure of the classified project to the Times.